As is well known, liquid or water drains or traps are employed in patient breathing systems to drain away liquid or water precipitated onto the inner sidewalls of the apparatus to prevent such liquid from pooling in low lying portions of the system and eventually entering the patient or producing an obstruction to gas flow in the system. In standard breathing systems, such as those employing a volume ventilator, for example, heated, humidified gas or air is cyclically introduced into the lungs of a patient to perform the breathing function for the patient or, in some cases, to assist the patient in breathing. In such systems, water condenses on the inner sidewalls of the breathing tubes. In some breathing systems, such as in aerosol therapy, air and a liquid such as water are used to produce a fine spray which is applied to the interior of the lungs to aid in mobilizing secretions. Medicaments such as antibiotics and bronchial medications may also be introduced by such aerosol therapy. In aerosol therapy apparatus, the liquid is precipitated in particulate form on inner sidewalls of the tubing, and a drain is used to prevent an accumulation of liquid.
Generally, in order to empty or open a water trap or drain to remove liquid or water from the breathing system without interrupting or interfering with the breathing function, various valve devices have been used. For example, a valve may be used to close a drain passage to a collection container. In such case, there is the possibility of foreign organisms entering the system because the container is removed for emptying the collected water. Also, in such cases, the container must generally be relatively small since the container normally is in fluid communication with the system gas supply and therefore adds to the system compliance or gas pressure loss of the system. The small collection container furthermore requires close attention and must be emptied often. In general, such drain valves are relatively complicated, expensive, and subject to mechanical failure.